Cob Bread Oven - The Upgrades!

This is the story of our second Cob Bread Oven.

We built the oven in week 2 (The Story of Trash) so that we could bake with it in week 3 (The Story of Food).

During Trash week of Stories of Household Items, our focus was on reuse, reduce, and recycle. We incorporated a number of reused materials into our oven, only buying concrete sand from Ready-Mix (total cost: $6).

In addition to sand, our oven included

old 55 gallon fiberboard drum donated by Emriver, Inc.

old glass bottles / sawdust / straw donated by Ms. Megan

old bricks from my garden wall

old newspapers from my house

clay dug from my yard

broken-up pieces of our first cob oven

leftover paper pulp from our Tuesday topic, The Story of Paper

Monday - build insulation layer and add sub floor

a 10 x 10 foot canopy to help protect the oven from rain

thank you to the family who donated this pop up canopy
during the COVID pandemic and our Outdoor School times!

Build Your Own Earth Oven, 3rd edition by Kiko Denzer

I cut down the drum so we could use it as a form
to hold the base layers while they were still wet

Step 2: Insulate Your Floor
p.41 - recycled glass bottles set in a "mortar" of clay slip + sawdust

working with Ms. Megan to mix it up

packing the bottles and mortar into our form

p.43 - heat sink - a bed of dense oven mix

dancing a batch of cob!

using the tarp to mix

p.52 - snowball test
p.53 - do the twist
p.54 - using a tarp to mix

Tuesday - let dry

Today we took a break from the oven so that the base layers could dry and did some Papermaking to go with our "recycle" theme. This colorful paper pulp was all left over from January's Capital Letters block (G is for Goose) -- see This Week in Papermaking -- and I froze it afterwards so that it wouldn't be wasted. After today I didn't want to re-freeze the remnants, so I got the brilliant idea of adding the pulp to the oven as part of the wet paper layer!

bags of frozen pulp thawing in the sink

Wednesday - build hearth, make sand form, add newspaper layer

before today's activities started, I cut the sides off the fiberboard drum
(this was super easy to do because it was wet)

fiberboard is NOT safe to burn so it MUST be removed from the final oven; however, using the drum was extremely helpful because then we could use the lid as a template to help us plan the hearth

Step 3: Make Your Hearth Floor
p.45 - spread a smooth shallow bed of sand on the subfloor

with the addition of the "tongue,"
the children thought he looked like a little man!

Step Five: Make the Sand Form, or Shape the Void

p.50 - "The oven is a void, and the sand form is what shapes it.
Cover the void with oven-mud, dig it out -- there's an oven!"

you cover the sand form with a layer of wet paper so that when you're tickling the sand away later your fingers can feel when to stop!

cob mixture contains quite a bit of sand so if you didn't have this shift in texture as a cue, you might remove quite a bit of your oven from the inside by mistake

Thursday - build oven mud layer

Thank you to Ms. Megan and her family for coming to help us again!

The children divided themselves into two teams of 7. One team was more interested in working with their feet and they went off to dig more clay, manipulate the tarp, and dance up a huge batch of cob. The other team was more interested in working with their hands and they stayed by the oven and added the cob when it came over in buckets.

Each team had time to sit in the shade and rest and drink water, of course! I was dancing cob and had absolutely no time to take pictures of that process!

p.55 - many handfuls make a layer

Friday & Saturday - let dry

Sunday - remove sand form

Thursday, Jun 20 - first baking attempt!

Baked Apples! The oven fired beautifully (much much better than our first attempt). Clean bright flames, smoke merrily coming out the chimney, and HOT. We cored apples and loaded fresh homemade butter, freshly ground nutmeg, and raw sugar into them, then wrapped them in aluminum foil (in case sand was still falling from the ceiling) and put them in for 1 1/4 hrs.

YUM!

If you're interested in cob ovens, here are some really nice notes from The Happy Monk Baking Company.

I will also add that I think you should make firm decisions about the roof and the door pretty early on, instead of hoping they will work themselves out later.

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